1. Field of the Invention.
The present invention relates to a method and apparatus for the culturing of cells, and in particular, it relates to a method and apparatus wherein the waste produced by the cultured cells is removed from the medium and preferably product produced by the cells is concentrated for harvesting.
2. Description of the Prior Art.
Perifusion culturing systems for the culturing of cells in-vitro are well known. The cells are fed nutrients and other factors using medium which is transported into a culturing chamber housing the cells and then is transported from the culturing chamber. The medium which contains nutrients and other factors is expensive and consequently such systems recirculate the medium since nutrients and other factors in the medium are not completely used in a single pass through the culturing chamber.
In addition to using the nutrients and other factors in the medium, the cells secrete waste products, such as lactic acid, into the medium. Over a period of time, the concentration of lactic acid builds up and has a deleterious effect on the cells. Waste products may inhibit a desired function, promote an undesired function, degrade or consume the product produced, or "kill" the cells or do all of the above or any combination of the above.
Typically, in the prior art systems, a batch exchange process is performed manually to replenish the medium with nutrients and other factors. Any product that was produced by the cells (which had been released into the medium) is separated from the medium by removing the medium and then performing a separate process to harvest the product. The process of removing the product is costly and time-consuming.